The present application relates generally to rotating machines and, more particularly, to methods and systems for use in isolating a frequency in a rotating machine.
At least some known rotating machines include one or more drive shafts that drive a load. During operation, a component of the machine, such as a gear or at least one bearing used to support the rotating drive shaft, may develop a flaw or a defect. Over time, continued operation with a “bad” component may cause the component to fail, which may cause degraded performance and/or damage to the machine. To facilitate preventing damage to the machine, such components are commonly monitored to detect performance issues that may be indicative of a component failure or component damage.
At least some known bearing monitoring systems execute an enveloping algorithm on an incoming signal, such as a vibration signal. More specifically, such algorithms enable bearing events to be identified via a transmission of impacts at a carrier frequency. The impacts are typically present in a spectrum with energy at the carrier frequency and with side bands that correspond to desired bearing frequencies. The enveloping process demodulates the signal resulting in a spectrum with energy at the desired bearing frequencies. Such an approach is generally more reliable for a machine that rotates with a constant speed. In contrast, if the machine speed varies, the bearing frequencies directly linked to the speed also vary which generally causes a “smearing” or obscuration of the spectrum. Such smearing clouds the frequencies of interest and makes identifying the bearing events difficult, if not impossible. Moreover, the variable speed may cause the energy to be present in unexpected frequency bins in the spectrum.